Methods, systems and tools with effectors are useful in particular for the precise adherence to work space boundaries during material and tissue removal with tools of rapidly rotating machine tools in surgery and in hand-crafting of free-form surfaces.
When hand-crafting in repair shops and in interventional medical treatment of humans and animals, manually-guided and manually-guided tools in form of driven machine tools (for example drill press with a drill or a milling tool, electrical planer) are frequently used for separating and removing material and tissue of an object. This is typically used, in addition to free-form shaping, for the spatial adaptation the object surface to a precisely fitting counterpart with defined boundaries. At the same time, certain structures or surfaces of the object must not be harmed with the tool, for example to protect an already finish-machined surface or structures inside the object, which are hidden from the view of the user.
To date, the following methods are known in the related art as technical aids for manually-guided and manually-positioned tools:
a) Navigation methods which measure the position and orientation of tools relative to object and graphically and acoustically indicate to the user the position, orientation and distance of the manually-guided tool to the allowed work space boundaries relative to object (Surgical Navigation, U.S. Pat. No. 5,389,101, DE 19960020) as well as graphically indicate the areas on the object that still need to be machined.
b) Template attached to the object for limiting the free movement of the manually-guided tool within the allowed work space boundaries relative to the object (Ancient Times, Middle Ages, Surgical Template U.S. Pat. No. 5,141,513).
c) Compliant mechanisms and robots, to which the manually-guided tool is attached. These mechanisms and robots change, relative to the allowed work space boundaries, the freedom, friction, stiffness and elasticity of the manually-guided movement on the object and apply even forces and torques in addition to the manual guidance (Lueth, T. C. et al., “A surgical robot system for maxillofacial surgery,” Industrial Electronics Society, 1998th IECON '98. Proceedings of the 24th Annual Conference of the IEEE, vol. 4, no., pp. 2470-2475).
d) Limiting the position, orientation, distance and signal-based removal rate relative to the object or structures of the object (Navigated Control, DE 000010117403C2).
e) Mechanisms for linearly deploying and retracting a rotating effector relative to a protective sleeve surrounding the effector (Blue Belt Technologies, US 2012/0123418A1) for limiting the removal rate.
Methods for adjusting of tool cutting edges are known from the published documents (DE 4401 496 A1), however not for handheld or manually-guided machine tools, whose movements of the tool position and the tool orientation cannot be definitely specified in advance by a program. No method is known that allows adjustment of the tool cutting edges without coupling to a programmable motion control. Likewise, no method is known that allows a computer-controlled or position-based adjustment of a rotating tool of a handheld or manually-guided machine tool.
A method to extend the cutting edges subsequent to wear of the cutting edges is known from EP 0977644B1.
With reference to the application of manually-guided driven tools with effectors in surgery, extensive experience has been gained over the last 20 years due to the increasing demand for efficiently fitting medical implants (e.g. knee, hip and the like). The disadvantages are similar to those encountered in hand-crafting of materials. The disadvantages of the present art are as follows:
a) Pure navigation methods with graphic, acoustic and tactile, vibrating feedback do not solve the problem, that the user inadvertently misaligns the material-removing tool due to a slip or lack of concentration and thus violates work space boundaries. The less time is available for learning and executing the applications, the greater is the risk. The risk increases when the material has different densities, the tool is deflected or the user works in an unergonomic posture and is subjected to shocks or forces.
b) Templates attached to the object require a sufficiently large available surface for attaching the template. In addition, templates exhibit their advantage primarily when the tool is inserted into the template in a preferred direction. It is currently not possible to mill a three-dimensional free-form surface while at the same time enabling three-dimensional mobility and three-dimensional orientation of the tools. Three-dimensional free-form surfaces can only be produced at great expense. Templates that cannot clearly be form-fittingly applied require navigation methods for aligning and affixing the templates to the object. Templates always require additional space on the object.
c) Compliant (compliant motion, hands-on) robots, on which the manually-guided instrument is attached, have a limited working space and must be aligned relative to the object prior to use in a complex process. During operation, hands-on robots allow a seemingly free movement of the instrument. The high inertia of the robot in relation to the manually-guided tool or object are a limiting factor for the precise adherence to work space boundaries even with optimal dynamic control of a highly dynamic drive. Robots are also expensive to procure and operate, require a dedicated space next the object, and have a large mass. They also must be covered under sterile working conditions.
d) Although the method for position-, orientation-, distance-, and signal-based control of the removal rate (navigated control) is indeed optimally suitable for adhering to the work space boundaries, a dynamically controllable change of the removal rate is still a prerequisite in order to compete in terms of time with a template or a mechanisms/robotic solution in the boundary area. Likewise, precise adherence to the work space boundaries can only be achieved when the removal rate of the tool has the steepest possible transition. Shutting off the power is currently problematic with pneumatic or electric drives due to the high mass inertia of the tool, because the force applied to the hand changes strongly during the switching operation.
e) The mechanism for reducing the removal rate by relative movement of a protective sleeve disposed around the effector makes it possible to limit the removal rate while keeping the rotation speed constant. However, because the protective sleeve is larger than the effector itself and can be blocked by the object surface, often only a fast retraction or deflection of the tool is possible in practice. Masses are here also moved. In addition, the relative movement must be compensated earlier or later by hand, which prevents a fast operation with high precision.